From U.S. Pat. No. 4,930,199 a method is known for manufacturing thin metal filaments by machining, shaving or cutting them off the end face of a thin metal foil coiled around a mandrel. This produces a bundle of nearly parallel filaments with a predominantly quadrilateral cross-section, the equivalent cross-section of which is between 15 and 150 .mu.m. depending on the thickness of the foil and the cutting speed of the shaving or cutting tool. By equivalent diameter is meant here the diameter of the circle which has the same surface area as the quadrilateral cross-section of the filament.
Since these machined filaments often have a lower tensile strength and are less straight than drawn filaments, they are difficult to process into filament yarns by twisting at the usual speeds.